The invention relates to a colour display tube comprising a glass envelope consisting of a display window, a cone and a neck, which envelope is provided, in the neck-cone transition part, with a number of reference studs on the outside of the envelope against which the system of deflection coils is placed.
Such a colour display tube is known from the article "30 AX-Self-aligning 110.degree. in-line colour T.V. display" in IEEE Transactions on Consumers Electronics, vol. CE-24, No. 3, August 1978, pp. 481-7. The positioning of the system of deflection coils relative to the glass envelope is obtained in the colour display tube described here by means of three studs on the cone which cooperate with studs on the inside of the system of deflection coils. These studs on the cone fix three reference points which, together with the clamping ring of the system of deflection coils around the neck, fix the common axis of the envelope and the system of deflection coils. In the production process of colour display tubes it has proved difficult to glue studs to the glass envelope. Because the studs form the reference points for the system of deflection coils and in each tube have a predetermined thickness, the studs should not work loose because in that case the reference points for the system of deflection coils would be lost. In the case of a wrong choice of the thickness of the stud or in the case of a choice of another type of system of deflection coils the studs must be easily removable from the tube to enable replacement by other studs having the correct thickness.